Commitments, Contingencies, Guarantees, and Others - Unfunded Lending Commitments: Contractual Amount and Carrying Value (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Unfunded lending commitments, contractual amount	$ 386,732	$ 401,474
Off-balance sheet lending commitment, carrying value	176	137
Credit Card
Loss Contingencies [Line Items]
Unused commitments to extend credit, contractual amount	349,594	363,446
Other excluding credit card
Loss Contingencies [Line Items]
Unused commitments to extend credit, contractual amount	35,836	36,454
Off-balance sheet lending commitment, carrying value	144	110
Advised line of credit	1,800	1,600
Letter of credit
Loss Contingencies [Line Items]
Standby letters of credit and commercial letters of credit, contractual amount	1,302	1,574
Off-balance sheet lending commitment, carrying value	$ 32	$ 27